Units and measurements and such 2.79 and 2.80
I don't see units other than 1 in 2.7 when setting the scene scale; I don't see mm or centimeters or meters (in the properties panel > scene tab)?  


  I can put all sorts of numbers and units in the dimension boxes and in
  response blender just changes these values to some random number/unit
  combination


Blender adjusts from Meters to Centimeters to Millimeters as needed I think, eg.: when you scale from 99cm to 100cm it changes to 1m automatically (in the N panel). 


  Then I attempted to add an EMPTY cube which seems to come out huge.So
  I attempted to resize it by changing the dimensions, but it seems that
  I can put all sorts of numbers and units in the dimension boxes


I don't see any dimensions boxes, just "scale" in the N properties panel, and "size" in the "empty" data tab of the properties panel.  I did notice the scale seems to be double what it should be, ie. mesh cube was 10cm but the empty cube was the same size, but says 5cm.  May be a bug or maybe a sort of radius measurment (measured from the origin)? Idk.
GL OP : )